Optical micrometer for measuring thickness of transparent wafers
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United States of America Patent
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May 19, 1998
Grant Date -
N/A
app pub date -
May 3, 1996
filing date -
May 3, 1996
priority date (Note) -
Expired
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Abstract
Techniques and systems for measuring absolute thickness, the total thickness variation, and electric resistivity of a semiconductor wafer in a nondestructive optical fashion. Optical absorption is used to measure the absolute thickness of a semiconductor wafer with a light source and a phototransceiver. The thickness is determined by comparing the amount of absorption to a calibrated amount. Coherent light interference is used to measure the total thickness variation of a substrate. Alternatively, both the absolute thickness and total thickness variation of the substrate can be measured based on light absorption using a CCD imaging device. The resistivity of a wafer sample can also be measured by using an alternating electrical signal.
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